Melt-processible, thermoplastic random copolyimides having recoverable crystallinity and associated processes

ABSTRACT

Random, melt-processible copolyimides are disclosed herein. These copolyimides are semicrystalline and exhibit recoverable (semi)crystallinity from their melts. Associated processes, which entail either solution polymerization or melt polymerization, for producing and fabricating these copolyimides into useful articles having a predetermined shape are also disclosed.

FIELD OF THE INVENTION

This invention relates to selected copolyimide compositions each ofwhich can be processed as a melt and which exhibit recoverablecrystallinity upon cooling from the melt. In preferred embodiments,these copolyimide compositions can also be produced in a melt via meltpolymerization.

BACKGROUND OF THE INVENTION

Polyimides constitute a class of valuable polymers being characterizedby thermal stability, inert character, usual insolubility in even strongsolvents, and high glass transition temperature (T_(g)) among others.Prior art discloses that their precursors have heretofore been polyamicacids, which may take the final imidized form either by thermal orchemical treatment.

Polyimides have always found a large number of applications requiringthe. aforementioned characteristics in numerous industries, andcurrently their applications continue to increase dramatically inelectronic devices, especially as dielectrics.

Different aspects regarding polyimides and copolyimides may be found ina number of publications, such as for example:

Sroog, C. E., J. Polymer Sci.: Part C, No. 16 1191(1967).

Sroog, C. E., J. Polymer Sci.: Macromolecular Reviews, Vol. 11, 161(1976).

Polyimides, edited by D. Wilson, H. D. Stenzenberger, and P. M.Hergenrother, Blackie, USA: Chapman and Hall, New York, 1990.

Several terms are defined below which are used in accordance with thepresent invention of high performance polyimides that possesssimultaneously the following desirable properties: high thermalstability, such that they can be processed in the melt, and whichexhibit recoverable semicrystallinity upon crystallization from themelt.

The term “melt-processible polyimide” means that the polyimide hassufficiently high thermoxidative stability and sufficiently low meltviscosity at temperatures at or above the melting point of the polyimidesuch that the polyimide can be processed in the melt to form a shapedobject (e.g., extruded into a pellet, etc.) without the polyimideundergoing any significant degradation.

The term “melt-polymerizable polyimide” means that the polyimide can beformed in a melt in the absence of solvent by reaction of its respectivemonomers (e.g., dianhydride(s) and diamine(s)) to form initiallypolyamic acid(s), which are subsequently converted to the polyimide.Furthermore, the polyimide produced has sufficiently high thermoxidativestability and sufficiently low melt viscosity at temperatures at orabove the melting point of the polyimide such that the polyimide can beprocessed in the melt to form a shaped object (e.g., extruded into apellet, etc.) without the polyimide undergoing any significantdegradation.

The term “DSC” is an acronym for differential scanning calorimetry, athermal analysis technique widely used for accurately determiningvarious thermal characteristics of samples, including melting point,crystallization point, and glass transition temperature. The acronym“DSC” is employed in text that follows below. The following definitionsof slow, intermediate, and fast crystallization kinetics and relatedterms are based upon behavior of a given sample during DSC analysisunder slow cooling, quench cooling, reheat, etc. scans during the DSCanalysis (see infra for details).

The term “slow crystallization kinetics” means that the crystallizationkinetics are such that, for a given copolyimide sample, the sample, whensubjected to DSC analysis, essentially does not show any crystallizationduring slow cooling (i.e., cooling at 10° C./minute) from its melt butdoes exhibit a crystallization peak on subsequent reheat. Furthermore,no crystallization occurs upon quench cooling.

The term “intermediate crystallization kinetics” means that thecrystallization kinetics are such that, for a given copolyimide sample,when subjected to DSC analysis, the sample exhibits some crystallizationon slow cooling and furthermore does exhibit some crystallization onreheat after slow cooling. Furthermore, there is no strong evidence forcrystallization occurring upon quench cooling.

The term “fast crystallization kinetics” means that the crystallizationkinetics are such that, for a given copolyimide sample, when subjectedto DSC analysis the sample does exhibit crystallization peaks in bothslow and quench cooling and furthermore no observable crystallizationpeak is seen on subsequent reheat of a given sample following slowcooling. After quench cooling, there may be some crystallizationexhibited on reheat.

The term “melt of a polymer” means the polymer exists as the melt in aliquid or substantially liquid state. If the polymer is crystalline orsemicrystalline, a melt of the polymer is necessarily at a temperaturegreater than or equal to its melting point (T_(m)).

The term “recoverable semicrystallinity” and/or “recoverablecrystallinity” refers to behavior occurring in a semicrystalline orcrystalline polymer and specifically means that behavior that occurswhen the polymer, upon heating to a temperature above its melting pointand subsequent slow cooling to a temperature well below its meltingpoint, exhibits a melting point in a reheat DSC scan. (If a meltingpoint is not observed during the reheat DSC scan, the polymer does notexhibit recoverable crystallinity. The longer a sample is below T_(m)but above T_(g), the greater probability it has to crystallize.)

The term “semicrystalline polymer” means a polymer that exhibits atleast some crystalline characteristics and is partially but notcompletely crystalline. Most or all known polymers having crystallinecharacteristics are semicrystalline, but not totally crystalline, sincethey also have at least some amorphous characteristics. (Hence the termcrystalline polymer is technically a misnomer in most or all instanceswhere it is used, but nevertheless is often used.)

The melt index of a polymer is defined to be the number of grams ofpolymer extruded at a specific temperature and load through a die of aspecified length and diameter in a time period often minutes. Details ofthe geometry and test procedures are described in ASTM D1238(ASTM=American Society for Testing and Materials).

Some significant advantages of melt processing of semicrystallinepolyimides having recoverable crystallinity according to the inventioninclude processing without a solvent such that tedious and costlysolvent recycling is unnecessary and can be eliminated. High thermalstability is not only essential for processing in the melt attemperatures of greater than or equal to 350° C. but also is requiredfor polyimides used in high temperature applications. Semicrystallinepolyimides are often highly desirable in comparison to otherwisecomparable polyimides that are amorphous, since the former in relationto the latter often exhibit superior properties, such as having bettermechanical properties (e.g., especially higher modulus), capability foruse at higher temperatures without property degradation (e.g., bettersolder resistance, modulus retention), higher solvent resistance, highercreep viscosities (e.g., lower tendencies for distortion of a film orother structure with time), and lower coefficients of thermal expansion.

In order for a semicrystalline polyimide to be consideredmelt-processible, the polyimide must possess a melting point below atemperature of about 385° C., which temperature is a practical limit formelt processing due to both equipment capabilities/limitations and toavoid any significant thermal degradation of the polyimide. Furthermore,the polyimide also must possess a sufficiently low melt viscosity (i.e.,less than or equal to a maximum of about 10⁸ poise (which is equal to10⁷ Pascal-seconds), but preferably 10⁴ poise (which is equal to 10³Pascal-seconds), depending on polymer melt temperature and shear ratesof the melt processing equipment). Copolymerization can be used to lowerthe melting temperature of a polymer (e.g., polyimide) but usuallyresults in loss of crystallinity. Prior art compositions have beenunable to achieve suitable reduction in the melting points (T_(m)s) ofthe copolymeric compositions while simultaneously maintainingsubstantial degrees of semi-crystallinity in the copolymericcompositions. In the compositions of this invention, both suitablemelting temperatures and substantial degrees of semi-crystallinity areachieved by judicious choice of comonomers and their relative amounts inthe compositions.

Polyimides that exhibit a melting point in an initial DSC heat scan andwhich are thereby attributed to have crystalline characteristics aredisclosed in Kunimune, U.S. Pat. No. 4,923,968 to Chisso Corporation.While the copolyimides disclosed in this patent may be crystalline orsemicrystalline until heated to temperatures above their melting points,the present inventors have not observed the copolyimides disclosed inthis patent to exhibit recoverable crystallinity. Indeed thesecopolyimides are probably substantially amorphous when cooled from theirmelts. Furthermore, many of the copolyimides disclosed in this patentare not melt-processible, because they have melting points, molecularweights, and/or melt viscosities that are too high formelt-processibility. In addition, endcapping in order to moderate thepolymerization and improve melt processibility is not taught.

The selected random copolyimides of this invention overcome thedrawbacks of the prior art compositions in that these copolyimidespossess simultaneously these key essential properties—high thermalstability, melt-processibility, and recoverable crystallinity. Thecopolyimides of this invention can therefore be processed in the melt toform articles, which may have a predetermined shape, such as extrudates,fibers, films, and molded products comprised of these semicrystallinecopolyimides. In many cases, the copolyimides of this invention can alsobe produced in the melt (via melt-polymerization).

There is a significant long-felt need not met by the current state ofpolyimide art for high performance polyimides that possess high thermalstability, which can be processed in the melt (melt-processible), andwhich exhibit recoverable semicrystallinity upon crystallization fromthe melt. This invention provides a solution to this long-felt need.There is also a long-felt need not met by the current state of polyimideart for high performance polyimides that can be produced by meltpolymerization of appropriate monomers in a melt. In many embodiments,this invention also provides a solution to this latter long-felt need.

SUMMARY OF THE INVENTION

In one embodiment, the invention is a melt-processible, thermoplasticcopolyimide comprising the reaction product of components comprising:

(I) an aromatic dianhydride component selected from the group consistingof 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA);

(II) an aromatic diamine component consisting essentially of:

(A) a first aromatic diamine selected from the group consisting of1,3-bis(4-aminophenoxy)benzene (APB-134) and 3,4′-oxydianiline(3,4′-ODA);

(B) a second aromatic diamine selected from the group consisting of1,3-bis(3-aminophenoxy)benzene (APB-133), 4,4′-oxydianiline (4,4′-ODA),1,3-diaminobenzene (MPD), 1,4-bis(4-aminophenoxy)benzene (APB-144),4,4′,bis(4-aminophenoxy)diphenyl sulfone (BAPS),4,4′-bis(4-aminophenoxy)-biphenyl (BAPB);2,2-bis(4-[4-aminophenoxyl]phenyl)propane (BAPP);bis(4-[4-aminophenoxy]phenyl ether (BAPP), 4,4′-oxydianiline (4,4′-ODA)and 1,3-diaminobenzene (MPD) in combination, and 4,4′-oxydianiline(4,4′-ODA) and 1,4-diaminobenzene (PPD) in combination;

 with the proviso that the second diamine is not the same as the firstdiamine; and

(III) an endcapping component;

wherein the copolyimide has a stoichiometry in the range from 93% to98%, exhibits a melting point in the range of 330° C. to 385° C., andexhibits recoverable crystallinity as determined by differentialscanning calorimetry analysis. While the present inventors have found nopolyimides having recoverable crystallinity outside the above-definedcompositional limits in combination with melt-processibility, somecompositions within the limits do not exhibit recoverable crystallinityand are therefore not within the scope of the present invention.

As used herein the term “stoichiometry”, expressed as a percent, meanstotal moles of dianhydride(s) in relation to total moles of diamine(s)that are incorporated in a given polyimide. If the total moles ofdianhydride(s) equals the total moles of diamine(s), the stoichiometryis 100 percent. If these two numbers are not equal, either totaldiamine(s) or total dianhydride(s) is present in higher amount, and thestoichiometery in this case is expressed as the mole percentage ofcomponent(s) (diamine(s) or dianhydride(s)) present in lesser amountrelative to that component(s) present in higher amount. As one example,if a polyimide sample is derived from incorporation of 0.98 mole ofdianhydride(s) and 1.00 mole of diamine(s), the diamine(s) is present inhigher amount and the stoichiometery is 98%.

As used herein the term “endcapping” refers to the monofunctionalcomponent(s) (agent(s)) including, but not limited to, phthalicanhydride, naphthalic anhydride, and aniline, which cap the copolyimidesto moderate the polymerization and to enhance thermoplasticity of thefinal melt polymerized product. Endcapping is generally done to 100%such that total moles of anhydride functionality are equal to totalmoles of amine functionality. Phthalic anhydride and naphthalicanhydride are suitable endcapping components in those cases wherediamines are present in greater molar amounts than are dianhydrides.Aniline is a suitable endcapping component in those cases wheredianhydrides are present in greater molar amounts than are diamines. Thepercentage of endcapping component required to afford 100% endcapping isequal to twice the value of (1−stoichiometry) multipled by 100. As anexample, for a 100% endcapped copolyimide with 95% stoichiometry(diamine in excess), the total moles of the endcapping agent must be 10mole percent of the total moles of the diamines, i.e., 10 moles of theendcapping agent to 100 moles of the diamines.

A given melt-processible copolyimide of the invention can in mostinstances be obtained by melt-polymerization or, alternatively, in allinstances by traditional solution polymerization techniques, the latterof which are well known in the art. The melt processing technique of theinvention can be used to manufacture an article of predetermined shape.

In the melt polymerization technique, the method of the inventioncomprises the steps of:

(a) blending, to substantial homogeneity, components comprising:

(I) 93 to 98 mole parts of an aromatic dianhydride component consistingessentially of 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA);

(II) 100 mole parts of an aromatic diamine component consistingessentially of:

(A) a first aromatic diamine selected from the group consisting of1,3-bis(4-aminophenoxy)benzene (APB-134) and 3,4′-oxydianiline(3,4′-ODA);

(B) a second aromatic diamine selected from the group consisting of1,3-bis(3-aminophenoxy)benzene (APB-133), 4,4′-oxydianiline (4,4′-ODA),1,3-diaminobenzene (MPD), 1,4-bis(4-aminophenoxy)benzene (APB-144),4,4′,bis(4-aminophenoxy)diphenyl sulfone (BAPS),4,4′-bis(4-aminophenoxy)-biphenyl (BAPB);2,2-bis(4-[4-aminophenoxyl]phenyl)propane (BAPP);bis(4-[4-aminophenoxy]phenyl ether (BAPE), 4,4′-oxydianiline (4,4′-ODA)and 1,3-diaminobenzene (MPD) in combination, and 4,4′-oxydianiline(4,4′-ODA) and 1,4-diaminobenzene (PPD) in combination;

 with the proviso that the second diamine is not the same as the firstdiamine; and

(III) 4 to 14 mole parts of at least one endcapping component;

the components (I), (II) and (III) being in substantially solventlessform and the blending step producing a substantially solventlesscomponent blend;

the blending step being carried out at a temperature below the meltingpoint of any of components (I), (II) and (III);

the components (I) and (II) being present in the component blend in amolar ratio of (I):(II) from 0.93 to 0.98;

the component (III) being present in the component blend in a molarratio (III):(II) of 0.04 to 0.14;

(b) heating the substantially solventless component blend produced instep (a) to a predetermined melt processing temperature at which the (I)aromatic dianhydride component and the (II) aromatic diamine componentare melted and will react to form a melt of a polyimide; thepredetermined melt processing temperature being less than thetemperature at which the polyimide melt chemically decomposes;

(c) mixing the component blend and the polyimide melt produced therefromduring the heating step (b);

(d) removing water of reaction from the component blend and thepolyimide melt produced therefrom during the heating step (b);

(e) forming the polyimide melt into an article having predeterminedshape; and

(f) cooling the article having predetermined shape to ambienttemperature;

wherein the polyimide exhibits a melting point in the range of 330° C.to 385° C., and the polyimide exhibits recoverable crystallinity asdetermined by DSC analysis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view drawing of a twin-screw extruder having aplurality of longitudinal barrel zones and vent port openings.

FIG. 2 is a plan view drawing of a twin-screw extruder.

DETAILED DESCRIPTION OF THE INVENTION

The melt-processible, thermoplastic copolyimides of this invention arethe reaction products of components comprising an aromatic dianhydridecomponent, an aromatic diamine component, and an endcapping component.

The aromatic dianhydride component is selected from the group consistingof BPDA and BTDA; BPDA is preferred.

The aromatic diamine component consists of a first aromatic diamine anda second aromatic diamine. The first aromatic diamine is selected fromthe group consisting of APB-134 and 3,4′-ODA. The second aromaticdiamine is selected from the group consisting of APB-133, 4,4′-ODA, MPD,APB-144, BAPS, BAPB, BAPE, BAPP, 4,4′-ODA and MPD in combination, and4,4′-ODA and PPD in combination; wherein APB-133, APB-144, 4,4′-ODA,BAPS, and 4,4′-ODA and MPD in combination are preferred. 4,4′-ODA, and4,4′-ODA and MPD in combination are most preferred.

Suitable endcapping components when diamine(s) are in excess include,but are not limited to, phthalic anhydride and naphthalic anhydride. Asuitable endcapping component when dianhydride(s) is in excess includes,but is not limited to, aniline. A given copolyimide is produced byreaction of the dianhydride and diamine components as well as theendcapping component to form initially a poly(amic acid). Depending uponspecific conditions, the poly(amic acid) can either be subsequentlyconverted to polyimide (as is typical when the poly(amic acid) is formedin solution) or the poly(amic acid) can be essentially simultaneouslyfurther transformed to polyimide as it is being formed (as is typicalunder melt polymerization conditions).

The copolyimides of this invention are characterized to besemicrystalline, to exhibit recoverable crystallinity, and to possessall essential properties in order for them to be melt-processible. Thereis criticality of several parameters that define these copolyimides inorder that they can possess all three of these key propertiessimultaneously. Critical parameters include choice of comonomers (e.g.,dianhydride(s) and diamine(s)), amounts of different comonomers, and thestoichiometry of diamine(s) and dianhydride(s) in relation to oneanother. Endcapping is also an important consideration in order toimprove molecular weight control and melt stability. With proper choicesof these critical parameters, the copolyimides possess essentialproperties for melt-processibility, including melting points in therange of 330° C. to 385° C. and sufficiently low melt viscosities (i.e.,less than about 10⁸ poise and preferably less than about 10⁴ poise) topermit melt processing. In addition, these copolyimides aresemicrystalline and also exhibit recoverable crystallinity, i.e., thesecopolyimides can be crystalline or maintain their ability to crystallizewhen cooled below their melting points from their respective melts. Thechoice of comonomer(s) and their ratios for these copolyimides isparticularly critical with respect to semicrystallinity and havingrecoverable crystallinity.

The stoichiometry of the inventive copolyimides is another criticalparameter and must be in the range from 93% to 98%. Either dianhydridesor diamine(s) can be in excess, but preferably diamines are in excessand the copolyimides are capped with an endcapping agent (endcappingcomponent). Suitable endcapping agents in cases where diamine(s) is inexcess include, but are not limited to, phthalic anhydride andnaphthalic anhydride (e.g., 2,3-naphthalic anhydride); phthalicanhydride is preferred (with diamine in excess). A suitable endcappingagent in cases where dianhydride(s) is in excess includes, but is notlimited to, aniline. A copolyimide of this invention havingstoichiometry higher than 98% will in general have too high a meltviscosity, while one having stoichiometry less than 93% will have poormechanical properties, particularly toughness and flexural endurance.Stoichiometry will also impact at least to some extent thecrystallization kinetics. Higher stoichiometry may generally translateto slower crystallization kinetics and to higher polymer viscosity(which results in lower polymer chain mobility).

For copolyimides of this invention where the aromatic dianhydridecomponent is BPDA, the first aromatic diamine of the aromatic diaminecomponent is APB-134, and the second aromatic diamine is 3,4′-ODA, themolar ratio of APB-134/3,4′-ODA is in the range from about 90/10 toabout 60/40. When the molar ratio of APB-134/3,4′-ODA is higher thanabout 90/10, the copolyimides are too high melting to be readilymelt-processible. When the molar ratio of APB-134/3,4′-ODA is lower thanabout 60/40, the copolyimides exhibit melting points that are too lowand/or do not possess recoverable crystallinity.

For copolyimides of this invention where the aromatic dianhydridecomponent is BPDA, the first aromatic diamine of the aromatic diaminecomponent is 3,4′-ODA, and the second aromatic diamine is APB-134, themolar ratio of 3,4′-ODA/APB-134 is in the range from about 95/5 to about60/40. When the molar ratio of 3,4′-ODA/APB-134 is higher than about95/5, the copolyimides are too high melting to be readily meltprocessible. When the molar ratio of 3,4′-ODA/APB-134 is lower thanabout 60/40, the copolyimides exhibit melting points that are too lowand/or do not possess recoverable crystallinity.

For copolyimides of this invention where the aromatic dianhydridecomponent is BPDA, the first aromatic diamine of the aromatic diaminecomponent is APB-134, and the second aromatic diamine is 4,4′-ODA, themolar ratio of APB-134/4,4′-ODA is in the range from about 90/10 toabout 75/25. When the molar ratio of APB-134/4,4′-ODA is higher thanabout 90/10, the copolyimides are too high melting to be readilymelt-processible. When the molar ratio of APB-134/4,4′-ODA is lower thanabout 75/25, the copolyimides may exhibit melting points that are toolow and/or do not possess recoverable crystallinity and/or anundesirable high melting phase may appear due to formation ofBPDA/4,4′-ODA homopolyimide segments.

For copolyimides of this invention where the aromatic dianhydridecomponent is BPDA, the first aromatic diamine of the aromatic diaminecomponent is APB-134, and the second aromatic diamine is MPD, the molarratio of APB-134/MPD is in the range from about 95/5 to about 85/15.When the molar ratio of APB-134/MPD is higher than about 95/5, thecopolyimides are too high melting to be readily melt-processible. Whenthe molar ratio of APB-134/MPD is lower than about 85/15, thecopolyimides may exhibit melting points too low and/or exhibit a highmelting phase (wherein melting points, if present, are too high formelt-processiblity).

For copolyimides of this invention where the aromatic dianhydridecomponent is BPDA, the first aromatic diamine of the aromatic diaminecomponent is APB-134, and the second aromatic diamine is X, wherein X isselected from the group consisting of BAPS, BAPB, BAPP, and BAPE, themolar ratio of APB-134/X is in the range from about 95/5 to about 75/25.When the molar ratio of APB-134/X is higher than about 95/5, thecopolyimides are too high melting to be readily melt-processible. Whenthe molar ratio of APB-134/X is lower than about 75/25, the copolyimidesexhibit melting points that are too low and/or do not possessrecoverable crystallinity.

For copolyimides of this invention where the aromatic dianhydridecomponent is BPDA, the first aromatic diamine of the aromatic diaminecomponent is APB-134, and the second aromatic diamine is APB-133, themolar ratio of APB-134/APB-133is in the range from about 95/5 to about85/15. When the molar ratio of APB-134/APB-133 is higher than about95/5, the copolyimides are too high melting to be readilymelt-processible. When the molar ratio of APB-134/APB-133 is lower thanabout 85/15, the copolyimides exhibit melting points that are too lowand/or do not possess recoverable crystallinity.

For copolyimides of this invention where the aromatic dianhydridecomponent is BPDA, the first aromatic diamine of the aromatic diaminecomponent is 3,4′-ODA, and the second aromatic diamine is 4,4′-ODA, themolar ratio of 3,4′-ODA/4,4′-ODA is in the range from about 85/15 toabout 70/30. When the molar ratio of 3,4′-ODA/4,4′-ODA is higher thanabout 85/15, the copolyimides are too high melting. When the molar ratioof 3,4′-ODA/4,4′-ODA is lower than about 70/30, the copolyimides exhibitmelting points that are too low and/or do not possess recoverablecrystallinity and/or may exhibit an undesirable high melting phase.

For copolyimides of this invention where the aromatic dianhydridecomponent is BPDA, the first aromatic diamine of the aromatic diaminecomponent is 3,4′-ODA, and the second aromatic diamine is APB-144, themolar ratio of 3,4′-ODA/APB-144 is in the range from about 95/5 to about65/35. When the molar ratio of 3,4′-ODA/APB-144 is higher than about95/5, the copolyimides are too high melting. When the molar ratio of3,4′-ODA/APB-144 is lower than about 65/35, the copolyimides exhibitmelting points that are too low and/or do not possess recoverablecrystallinity and/or may exhibit an undesirable high melting phase.

For copolyimides of this invention where the aromatic dianhydridecomponent is BPDA, the first aromatic diamine of the aromatic diaminecomponent is 3,4′-ODA, and the second aromatic diamine is Y, wherein Yis selected from the group consisting of BAPS, BAPB, BAPE, and BAPP, themolar ratio of 3,4′-ODA/Y is in the range from about 95/5 to about80/20. When the molar ratio of 3,4′-ODA/Y is higher than about 95/5, thecopolyimides are generally too high melting for good meltprocessibility. When the molar ratio of Y/3,4′-ODA is lower than about80/20, the copolyimides may exhibit melting points that are too lowand/or do not possess recoverable crystallinity.

For copolyimides of this invention where the aromatic dianhydridecomponent is BPDA, the first aromatic diamine of the aromatic diaminecomponent is 3,4′-ODA, and the second aromatic diamine is APB-133, themolar ratio of 3,4′-ODA/APB-133 is in the range from about 95/5 to about85/15. When the molar ratio of 3,4′-ODA/APB-133 is higher than about95/5, the copolyimides are too high melting to be readilymelt-processible. When the molar ratio of 3,4′-ODA/APB-133 is lower thanabout 85/15, the copolyimides do not exhibit recoverable crystallinity.

For copolyimides of this invention where the aromatic dianhydridecomponent is BPDA, the first aromatic diamine of the aromatic diaminecomponent is APB-134, the second aromatic diamine is 4,4′-ODA and MPD incombination, the molar parts of APB-134/4,4′-ODA/MPD can range fromabout 95/2.5/2.5 to about 75/20/5. When the molar parts of 4,4′-ODA andMPD are both lower than about 2.5, the copolyimides are too high meltingto be readily melt-processible. When the molar parts of 4,4′-ODA and MPDare higher than about 20 and about 5, respectively, the copolyimidesexhibit melting points that are too low and/or do not possessrecoverable crystallinity and/or they may exhibit a high melting phase.

For copolyimides of this invention where the aromatic dianhydridecomponent is BPDA, the first aromatic diamine of the aromatic diaminecomponent is APB-134, the second aromatic diamine is 4,4′-ODA and PPD incombination, the molar parts of APB-134/4,4′-ODA/PPD can range fromabout 90/5/5 to about 70/20/10. When the molar parts of 4,4′-ODA and PPDare both lower than about 5, the copolyimides are too high melting to bereadily melt-processible. When the molar parts of 4,4′-ODA and PPD arehigher than about 20 and about 10, respectively, the copolyimides mayexhibit a high melting phase or may not possess readily recoverablecrystallinity.

For copolyimides of this invention where the aromatic dianhydridecomponent is BPDA, the first aromatic diamine of the aromatic diaminecomponent is 3,4′-ODA, the second aromatic diamine is 4,4′-ODA and PPDin combination, the molar parts of 3,4′-ODA/4,4′-ODA/PPD can range fromabout 95/2.5/2.5 to about 70/20/10, respectively. When the molar partsof 4,4′-ODA and PPD are both lower than about 2.5, the copolyimides aretoo high melting to be readily melt processible. When the molar parts of4,4′-ODA and PPD are higher than about 20 and about 10, respectively,the copolyimides exhibit melting points that are too low and/or do notpossess high levels of recoverable crystallinity and/or they may exhibita high melting phase.

For copolyimides of this invention where the aromatic dianhydridecomponent is BTDA, the first aromatic diamine of the aromatic diaminecomponent is APB-134, and the second aromatic diamine is APB-133, themolar ratio of APB-134/APB-133 is in the range from about 20/80 to about45/55. When the molar ratio of APB-134/APB-133 is higher than about45/55, the copolyimides are too high melting to be readilymelt-processible. When the molar ratio of APB-134/APB-133 is lower thanabout 20/80, the copolyimides exhibit melting points that are too lowand/or do not possess recoverable crystallinity.

The melt-processible, semicrystalline copolyimides of this invention aretypically produced by reaction between the aromatic dianhydridecomponent, the aromatic diamine component, and the endcapping component.As an illustrative but non-limiting example, the aromatic dianhydridecomponent can be BPDA, the first aromatic diamine can be APB-134, andthe second aromatic diamine can be 4,4′-ODA, wherein the molar ratio ofAPB-134/4,4′-ODA is chosen to be less than or equal to 90/10 but greaterthan or equal to 75/25, and the endcapping component can be phthalicanhydride.

As illustrated in many textbooks and other references (e.g., forexample, see Polyimides, edited by D. Wilson, H. D. Stenzenberger, andP. M. Hergenrother, Blackie, USA: Chapman and Hall, New York, 1990),reaction of a dianhydride(s) with a diamine(s) in solution initiallyaffords a poly(amic acid). Typical, but non-limiting, reactiontemperatures are ambient temperature to about 100° C. The poly(amicacid) that results can subsequently be converted to the correspondingpolyimide (and water) by either heating the poly(amic acid) to elevatedtemperature(s) (e.g., about 250-400° C.) and/or subjecting the poly(amicacid) to chemical imidization using reagents such as triethylamine incombination with acetic anhydride. These are two step processes ofobtaining a polyimide and require the removal of solvent for processinginto usable forms such as thin films and sheet products.

Another method of forming a polyimide is to form it directly by blendingand reacting comonomers (dianhydride(s), diamine(s), and endcappingagent(s)) at elevated temperatures in the absence of a solvent. Thismethod is melt polymerization. In this case, the comonomers react undercontinually increasing reaction temperatures and form poly(amic acid)which is, within a short time interval, essentially completely convertedto polyimide and water, such that there is in effect no substantialbuildup of poly(amic acid) in the reaction mixture. This method can beconducted under batch or continuous conditions, with continuousconditions being preferred for high volume. Under preferred conditions,this method is conducted continuously with monomers being fed into aninlet end of a continuous reactor having increasing temperature zonesand which is maintained at elevated temperatures above the melting pointof the polyimide being produced and reaction occurs with removal ofby-product water such that essentially pure polyimide as a melt exits atthe other (exit) end of the continuous reactor. Upon exiting thereactor, one or more other unit operations can be performed on the meltof the polyimide, which can afford an object having a predeterminedshape. These include, but are not limited to, casting the polyimide intoa film, a fiber, a sheet, a tube, an extrudate strand that is cut into apellet, a coating on a wire, a compression-molded article, and ablow-molded article.

Additional Melt Polymerization Details

In some embodiments, this invention provides for a melt polymerizationproduction of linear polyimides by reaction of certain aromatic diamineswith certain aromatic dianhydrides, with an endcapping component alsobeing present, at elevated temperature in the absence of any solvent.Melt polymerization, largely a solventless process, therefore producesthermoplastic polyimides without the need for solvents, as is requiredfor current ones prepared by the classical solvent-based two-stepapproach or, in the case of soluble polyimides, by single stage hightemperature solution polymerization using solvent/azeotroping agentsystems. With the exclusion of BTDA, any inventive combination ofmonomers in any stoichiometry that yields a melt index greater thanabout three (3) at temperatures up to the decomposition temperature ofthe polymer is feasible for use in melt polymerization embodiments ofthis invention. An endcapping agent (component) is incorporated tomoderate the polymerization and to enhance thermoplasticity of the finalmelt polymerized product.

Melt polymerization can be a batch process in a reactor, or a continuousprocess in an extruder or continuous mixer, or some combination tocomplete the melt polymerization in single pass or multiple passes.Polyimides made by either process may be amorphous, semicrystalline, andcrystallizable compositions that are also melt processible, thus may bedirectly processed to yield a variety of useful shaped articlesincluding films, coatings, tubing, adhesives, laminates, fibers,reinforced composites, tapes, molded parts and associated applicationsincluding electronic packaging, wire insulation and bearings. Or, theprocess may produce a resin in pellet form (also a shaped article) thatcan be secondarily processed into any or all of these same products atthe same or alternate facilities. These pellets may be shipped, storedand handled much like any other polymer without the need for specialrequirements for some current intermediate polyimide solutions. Thisinvention also yields a polyimide production process that is moreenvironmentally friendly without the solvents and their handling,containment and recovery issues. And, the ability to melt this productalso suggests the possibility of facile recycling, which is currentlypossible but very tedious and inconvenient.

A preferred melt polymerization process is a continuous one using anextruder, either twin-screw or single-screw, although a twin-screw witha plurality of longitudinal barrel zones is preferred. Suitablecombinations (e.g., as disclosed elsewhere in the specification and/oras exemplified in the examples) of the aromatic diamines with thearomatic dianhydrides are directly fed continuously into the extruderwhere they are melted, mixed and reacted to yield a molten polyimide.These ingredients may be fed into the extruder in one of several ways;individually with loss-in-weight feeders into a single feed point or atseparate points, as a pre-blended single feed from either volumetric orloss-in-weight feeders, and/or some combination of partially pre-blendedand individual ingredients in a single pass process. A multiple passprocess to complete the melt polymerization is also possible. Theextruder barrel zones are progressively increased in temperature toallow the reaction process to proceed in sequence until molten polymerflows freely out of the die. Extruder screws are designed to provide thenecessary feed and melt conveying, melting and mixing (such as kneadingblocks or mixers), and pumping to suit the process and residence time.Vent port openings along the way, combined with properly placed sealingelements (such as reverse flighted elements) in the screw to createpartially filled zones at these vent ports, are employed to continuouslyremove the by-product water of reaction.

Illustratively, FIG. 1 depicts in a side view schematically a typicaltwin-screw extruder having a plurality of longitudinal barrel zones andvent port openings that are set-up in one of several possiblearrangements. FIG. 2 illustrates a plan view of the two screws 4 of thetwin-screw extruder.

A general description of the reactive extrusion melt polymerizationprocess of this invention is given immediately below (for anillustrative, non-limiting case of a continuous reaction in an extruder)and specific cases are exemplified in some examples. The monomers, keptunder an inert atmosphere, are fed continuously at the prescribed ratesand compositional ratios through a closed connection, 1, into anextruder feed port opening 2. Heating and cooling means (not shown) areprovided along the barrel 3, for controlling the various zones depictedin order to control the reaction process as it proceeds through theextruder. The extruder feed zone 30 is kept at or below roomtemperature, while the immediate adjacent zone 31 is generally below thelowest melting point of the various formulation ingredients, as low as50° C., so as to avoid adversely impacting ingredient feed. Theremaining zone temperatures are then progressively increased withincrease in ascending zone number (as labeled in FIG. 1) to attain themelt polymerization temperature of the particular polyimide being formedand to achieve conveyance of the mixture through the remainder of theextruder zones and steady molten polymer flow through the die discharge.The zones maintained at elevated temperatures (except for zones 30 and31) may range from as low as about 100° C. to as high as about 380° C.FIG. 1 illustrates an extruder having a feed zone 30 and sevenadditional zones (31-37). The temperature of die 38 during meltpolymerization may be as high as 400° C., but is preferably maintainedin the 340° C. to 380° C. range.

The extruder screws 4 are rotated at a rotation speed (measured as RPM)chosen to provide sufficient residence time to complete the reactionprocess of polyimide formation via melt polymerization. Extruder screwrotation speeds can range from as low as about 50 RPM to as high asabout 500 RPM, although a rotation speed in the range from about 100 RPMto about 250 RPM is preferred. As is known to one skilled in the art ofextrusion technology, optimal choice of extruder screw speed is alsodependent on the screw element types and their positioning, as well asingredient composition and throughput rates used, and these extruderscrews are designed to provide the necessary feed and melt conveying,depicted as 9 in FIGS. 1 and 2, melting and mixing (such as kneadingblocks or mixers, 10), and pumping, 9, to suit the process and residencetime.

Vent port openings, (5, 6, 7 and 8 as illustrated in FIG. 1), along thelength of the extruder are employed to continuously remove thesubstantial amount of water of reaction produced as a co-product in themelt polymerization process. This water is efficiently removed bycontinuous venting through several vent ports that are spaced along theextruder. Normally, at least two vent ports are required but there canbe additional vent ports, i.e., four or even more can be employed. Ithas also been demonstrated that the first one or two ports removes themajority of the water of reaction at low vacuum, or even atmosphericpressure. The additional port(s) is preferably operated under vacuum toremove any additional water of reaction and/or bubbles that may beformed. Also, as is known to one skilled in the art of extrusiontechnology, there are special screw elements located immediately priorto these ports to completely fill the elements thereby creating a meltseal to limit the amount of polymer flow under the port to maximize theefficiency of water and/or bubble removal and to prevent plugging of theport. These include kneading blocks 10, or reverse flights, depicted as11 in FIG. 2, which create back pressure on the polymer to fill theelements. Placement of the vent ports is determined by the formulationand throughput rates used relative to the screw elements and screwspeed.

This process may be used to yield predetermined shapes of a variety ofuseful articles including films, coatings, tubing, adhesives, laminates,fibers, reinforced composites, tapes, molded parts and associatedapplications including electronic packaging, wire insulation andbearings. Or, the process may produce a resin in pellet form that can besecondarily processed into any or all of these same products at the sameor alternate facilities.

In most cases, the melt polymerization process of this invention is afirst pass production process. Alternatively, the melt polymerizationprocess can be a multiple step process, in which case the process ispreferably two steps. In this latter case, the first step meltpolymerization can yield a low molecular weight polymer. The second stepinvolves melt polymerizing a mixture of this low molecular weightpolymer with the addition of a sufficient amount of at least one othermonomer to produce the desired stoichiometry and molecular weight.Conceptually, this second step can be directly coupled to the first meltpolymerization device, or uncoupled and done off-line at a later timeand/or another facility. This two-step process may be advantageous,and/or preferred, when that second step is used to produce a finalproduct conducive to an extrusion type process, such as film, coatedwires, tubing, and fiber.

GLOSSARY

Diamines

APB-133—1,3-bis(3-aminophenoxy)benzene

APB-134—1,3-bis(4-aminophenoxy)benzene (=RODA)

APB-144—1,4-bis(4-aminophenoxy)benzene

BAPB—4,4′-bis(4-aminophenoxy)-biphenyl

BAPE—bis(4-[4-aminophenoxy]phenyl ether(=4,4′-bis(4-aminophenoxy)-diphenylether)

BAPP—2,2-bis(4-[4-aminophenoxyl]phenyl)propane

BAPS—4,4′,bis(4-aminophenoxy)diphenyl sulfone

MPD—1,3-diaminobenzene

PPD—1,4-diaminobenzene

3,4′-ODA—3,4′-oxydianiline

4,4′-ODA—4,4′-oxydianiline

3,3′-ODA—3,3′-oxydianiline

RODA—1,3-bis(4-aminophenoxy)benzene (=APB134)

2Ph-APB-144—2-phenyl-1,4-bis(4-aminophenoxy)benzene

Dianhydrides

BPDA—3,3′4,4′-biphenyltetracarboxylic dianhydride

BTDA—3,3′4,4′-benzophenone tetracarboxylic dianhydride

General

AA—Acetic anhydride

CTE—Coefficient of thermal expansion

DSC—Differential scanning calorimetry

hr(s)—hour(s)

lb(s)—pound(s)

RPM—Revolutions per minute

TEA—Triethylamine

g—gram

GPa—Gigapascals

GPC—Gel permeation chromatography

MI—Melt Index (or melt flow index or melt flow rate)

J/g—Joules per gram

M_(n)—Number average molecular weight (determined by GPC unlessotherwise indicated)

M_(w)—Weight average molecular weight (determined by GPC unlessotherwise indicated)

MPa—Megapascal

PA—Phthalic anhydride

RPM—Revolutions per minute

T_(g)—Glass transition temperature

T_(m)—Melting point (° C. unless otherwise specified)

Polyimide M/N/O/P w/x/y/z Polyimide that is reaction product of M at wparts, N at x parts, O at y parts, and P at z parts, where M,N,O, and Pare monomers and all parts are mole parts (unless otherwise indicated)

Solvents

DMAC—N,N-dimethylacetamide

NMP—N-methyl-2-pyrrollidinone

SELECTED DIANHYDRIDE STRUCTURES Dianhydride Dianhydride Structure BPDA

BTDA

EXAMPLES

All percentages are mole percentages unless otherwise indicated. Allparts are molar parts unless otherwise indicated. All ratios are molarratios unless otherwise indicated. All temperatures are in degreesCentigrade (° C.) unless otherwise indicated. The phrase “a melt of apolyimide” is equivalent to the phrase “a polyimide melt”.

A standard DSC testing protocol was utilized as indicated for specificexamples. A description of this standard DSC testing protocol follows:

A given powder polyimide sample was subjected to DSC analysis todetermine melting point, glass transition temperature, andcrystallization characteristics of the sample in relation to itsstructural characteristics. An initial DSC analysis at 20° C./minutefrom ambient temperature to 500° C. was done to determine theappropriate upper temperature limit (T_(ul)) for the sample to bebrought to during the multiple scan DSC analysis. This T_(ul) was chosento be below the temperature above which appreciable decomposition wouldoccur, but above the temperature(s) of all significant transitions(melting, glass transition, etc.).

In each case, unless otherwise indicated a fresh sample was used in themultiple scan DSC, keeping the maximum temperature attained in the scanbelow T_(ul). The multiple scan DSC was run in the following manner:

1) An initial heat scan from ambient temperature to T_(ul) at 10°C./minute.

2) A slow cool scan from T_(ul) to ambient temperature at 10° C./minute.

3) A second heat scan from ambient temperature to T_(ul) at 10°C./minute.

4) A quench cool scan from T_(ul) to ambient temperature. (Quench coolscan was done by placing a dry ice dewar on top of the DSC cell to allowcooling at a fast but uncontrolled rate.)

5) A third heat scan from ambient temperature to 500° C. at 10°C./minute. All DSC measurements (unless otherwise indicated) wereobtained on a DuPont 9900 DSC unit (E. I. du Pont de Nemours andCompany, Wilmington, Del.). DuPont's former DSC business is now owned byTA Instruments, Wilmington, Del.

For the DSC analysis of each of the polyimide samples from Examples18-20, an automated multiple scan DSC analysis was run in the followingmanner:

Sample is heated and equilibrated to 80° C.

An initial heat scan is run from 80° C. to 415° C. at 10°C./minute.

The sample is held at 415° C. for 6 minutes.

A slow cool scan is run from 415° C. to 80° C. at 10° C./minute.

A second heat scan is run from 80° C. to 415° C. at 10° C./minute.

All DSC measurements were obtained on a TA Instruments A-2920 DSC unit(Thermal Analysis Instruments Company, New Castle, Del.)

All of the melt index numbers reported or referenced herein weredetermined under a load of 8,400 grams at the specified temperature,i.e., either 350° C. or 375° C., and were conducted on a commercialautomated melt index tester, or plastometer, a Tinius-Olsen ExtrusionPlastometer Model MP-993.

EXAMPLES Example 1 Preparation of Polyimide Based onBPDA//3,4′-ODA/APB-134//PA 95//70/30//10(95% —of StoichiometricDianhydride)

Into a 250 ml round bottom flask equipped with a mechanical stirrer andnitrogen purge were charged 5.3695 g (0.02681 mole) of diamine 3,4′-ODA,3.3596 g (0.01149 mole) of diamine APB-134 and 60 ml of NMP. Afterdissolution of the diamines, 10.7073 g (0.03639 mole) of dianhydrideBPDA and 0.5674 g (0.00383 mole) phthalic anhydride were added withstirring under nitrogen and rinsed in with 20 ml NMP. The following day,14.46 ml (0.153 mole) of acetic anhydride (4×moles of diamine) and 21.36ml (1.53 mole) of triethylamine (4×moles of diamine) were added to thepoly(amic acid) solution to effect imidization. After about 10 minutesthe polymer precipitated, any clumps were broken up by manualmanipulation of the mechanical stirrer, and stirring was continued forabout 6 hours. The resulting polymer slurry was then added to methanolin a blender to complete precipitation and remove NMP. The polymer wasseparated by filtration, washed with methanol, and then dried at ca.200° C. overnight under vacuum with a nitrogen bleed. DSC analysis (10°C./min.) of the resulting polyimide showed a melting point of 345° C.during the first heating scan, a crystallization exotherm upon thesubsequent cooling scan at 296° C., and a melting point at 346° C.during the subsequent reheat scan, indicating recoverable crystallinityfrom the melt.

Example 2 Preparation of Polyimide Based on BPDA//3,4′-ODA/APB-134//PA95//75/25//10—(95% of Stoichiometric Dianhydride)

In a similar manner to Example 1, a polyimide was prepared with 10.8026g BPDA, 5.8042 g 3,4′-ODA, 2.8246 g APB-134 and 0.5727 g phthalicanhydride. DSC analysis (10° C./min) of the resulting polyimide showed amelting point of 354° C. during the first heating scan, acrystallization exotherm upon the subsequent cooling scan at 298° C.,and a melting point of 354° C. during the subsequent reheat scan,indicating recoverable crystallinity from the melt.

Example 3 Preparation of Polyimide Based on BPDA//3,4′-ODA/APB-134//PA95//80/20//10—(95% of Stoichiometric Dianhydride)

In a similar manner to Example 1 a polyimide was prepared with 10.8996 gBPDA, 6.2468 g 3,4′-ODA, 2.2799 g APB-134 and 0.5776 g phthalicanhydride. DSC analysis (10° C./min) of the resulting polyimide showed amelting point of 362° C. during the first heating scan, acrystallization exotherm upon the subsequent cooling scan at 295° C.,and a melting point of 362° C. during the subsequent reheat scan,indicating recoverable crystallinity from the melt.

Example 4 Preparation of Polyimide Based on BPDA//3,4′-ODA/4,4′-ODA//PA95//80/20//10—(95% of Stoichiometric Dianhydride)

In a similar manner to Example 1 a polyimide was prepared with 11.3056 gBPDA, 6.4795 g 3,4′-ODA, 1.6199 g 4,4′-ODA and 0.5991 g phthalicanhydride. DSC analysis (10° C./min) of the resulting polyimide showed amelting point of 382° C. during the first heating scan, acrystallization exotherm upon the subsequent cooling scan at 302° C.,and a melting point of 382° C. during the subsequent reheat scan,indicating recoverable crystallinity from the melt.

Example 5 (Comparative) Preparation of Polyimide Based onBPDA//3,4′-ODA/4,4′-ODA/MPD//PA 95//75/15/10//10—(95% of StoichiometricDianhydride)

In a similar manner to Example 1 a polyimide was prepared with 11.5202 gBPDA, 6.1898 g 3,4′-ODA, 1.2380 g 4,4′-ODA, 0.4457 g MPD and 0.6105 gphthalic anhydride. DSC analysis (10° C./min) of the resulting polyimideshowed a melting point of 354° C. during the first heating scan, acrystallization exotherm upon the subsequent cooling scan at 334° C. anda melting point of 298° C. during the subsequent reheat scan, indicatingonly partially recoverable crystallinity from the melt. The meltingtransition during reheat was, however notably reduced in enthalpyindicating MPD's detrimental effect in the composition on recoverablecrystallinity from the melt when compared to Example 4.

Example 6 (Comparative) Preparation of Polyimide Based onBPDA//3,4′-ODA/4,4′-ODA/MPD//PA 95//80/10/10//10—(95% of StoichiometricDianhydride)

In a similar manner to Example 1 a polyimide was prepared with 11.5202 gBPDA, 6.6025 g 3,4′-ODA, 0.8253 g 4,4′-ODA, 0.4457 g MPD and 0.6105 gphthalic anhydride. DSC analysis (10° C./min) of the resulting polyimideshowed a melting point of 350° C. during the first heating scan, nocrystallization exotherm upon the subsequent cooling scan and only a Tg(255° C.) during the subsequent reheat scan, indicating MPD'sdetrimental effect in the composition on recoverable crystallinity fromthe melt when compared to Example 4.

Example 7 (Comparative) Preparation of Polyimide Based onBPDA//3,4′-ODA/4,4′-ODA/MPD//PA 95//75/20/5//10—(95% of StoichiometricDianhydride)

In a similar manner to Example 1 a polyimide was prepared with 11.4119 gBPDA, 6.1316 g 3,4′-ODA, 1.6351 g 4,4′-ODA, 0.2208 g MPD and 0.6048 gphthalic anhydride. DSC analysis (10° C./min) of the resulting polyimideshowed a melting point of 343° C. during the first heating scan, nocrystallization exotherm upon the subsequent cooling scan, and only a Tg(255° C.) during the subsequent reheat scan, indicating MPD'sdetrimental effect in the composition on recoverable crystallinity fromthe melt when compared to Example 4.

Example 8 (Comparative) Preparation of Polyimide Based onBPDA//3,4′-ODA/APB-133//PA 95//80/20//10—(95% of StoichiometricDianhydride)

In a similar manner to Example 1 a polyimide was prepared with 10.8996 gBPDA, 6.2468 g 3,4′-ODA, 2.2799 g APB-133, and 0.5775 g phthalicanhydride. DSC analysis (10° C./min) of the resulting polyimide showed amelting point of 342° C. during the first heating scan, nocrystallization exotherm upon the subsequent cooling scan, and only a Tg(230° C.) during the subsequent reheat scan, indicating APB-133'sdetrimental effect at this level on recoverable crystallinity from themelt when compared to Example 3.

Example 9 Preparation of Polyimide Based on BPDA//3,4′-ODA/APB-144//PA95//80/20//10—(95% of Stoichiometric Dianhydride)

In a similar manner to Example 1, a polyimide was prepared with 10.8974g BPDA, 6.2455 g 3,4′-ODA, 2.2795 g APB-144 and 0.5774 g phthalicanhydride. DSC analysis (10° C./min) of the resulting polyimide showed amelting point of 363° C. during the first heating scan, acrystallization exotherm upon the subsequent cooling scan at 306° C.,and a melting point of 356° C. during the subsequent reheat scan,indicating recoverable crystallinity from the melt.

Example 10 Preparation of Polyimide Based on BPDA//3,4′-ODA/APB-144//PA95//75/25//10—(95% of Stoichiometric Dianhydride)

In a similar manner to Example 1 a polyimide was prepared with 10.8005 gBPDA, 5.8031 g 3,4′-ODA, 2.8240 g APB-144 and 0.5723 g phthalicanhydride. DSC analysis (10° C./min) of the resulting polyimide showed amelting point of 360° C. during the first heating scan, acrystallization exotherm upon the subsequent cooling scan at 318° C.,and a melting point of 354° C. during the subsequent reheat scan,indicating recoverable crystallinity from the melt.

Example 11 Preparation of Polyimide Based on BPDA//3,4′-ODA/APB-144//PA95//70/30//10—(95% of Stoichiometric Dianhydride)

In a similar manner to Example 1, a polyimide was prepared with 10.7053g BPDA, 5.3685 g 3,4′-ODA, 3.3590 g APB-144 and 0.5673 g phthalicanhydride. DSC analysis (10° C./min) of the resulting polyimide showed amelting point of 359° C. during the first heating scan, acrystallization exotherm upon the subsequent cooling scan at 320° C.,and a melting point of 358° C. during the subsequent reheat scan,indicating recoverable crystallinity from the melt.

Example 12 (Comparative) Preparation of Polyimide Based onBPDA//3,4′-ODA/APB-1 44//PA 95//60/40//10—(95% of StoichiometricDianhydride)

In a similar manner to Example 1, a polyimide was prepared with 10.5197g BPDA, 4.5218 g 3,4′-ODA, 4.4010 g APB-144 and 0.5575 g phthalicanhydride. DSC analysis (10° C./min) of the resulting polyimide showedmelting points of 367° C. and 386° C. during the first heating scan, acrystallization exotherm upon the subsequent cooling scan at 329° C.,and melting points of 367° C. and 387° C. during the subsequent reheatscan, indicating recoverable crystallinity from the melt, but too highmelting point characteristics.

Example 13 (Comparative) Preparation of Polyimide Based onBPDA//3,4′-ODA/3,3′-ODA//PA 95//30/70//10—(95% of StoichiometricDianhydride)

In a similar manner to Example 1, a polyimide was prepared with 11.3056g BPDA, 5.6695 g 3,3′-ODA, 2.4298 g 3,4′-ODA and 0.5991 g phthalicanhydride. DSC analysis (10° C./min) of the resulting polyimide showedno melting point during the first and only heating scan and a Tg of 230°C., indicating the polyimide possessed little or no semi-crystallinity.

Example 14 (Comparative) Preparation of Polyimide Based onBPDA//3,4′-ODA/3,3′-ODA//PA 95//70/30//10—(95% of StoichiometricDianhydride)

In a similar manner to Example 1, a polyimide was prepared with 11.3056g BPDA, 5.6695 g 3,4′-ODA, 2.4298 g 3,3′-ODA and 0.5991 g phthalicanhydride. DSC analysis (10° C./min) of the resulting polyimide showedno melting point during the first and only heating scan and a Tg of 247°C., indicating the adverse impact of 3,3′-ODA on crystallinity whencompared to Example 11.

Example 15 (Comparative) Preparation of Polyimide Based onBPDA//3,4′-ODA/MPD//PA 95//90/10//10—(95% of Stoichiometric Dianhydride)

In a similar manner to Example 1, a polyimide was prepared with 11.5202g BPDA, 7.4278 g 3,4′-ODA, 0.4457 g MPD and 0.6105 g phthalic anhydride.DSC analysis (10° C./min) of the resulting polyimide showed a meltingpoint of 365° C. during the first heating scan, no crystallizationexotherm upon the subsequent cooling scan, and no melting point duringthe subsequent reheat scan, indicating MPD's detrimental effect onrecoverable crystallinity from the melt when compared to severalprevious examples (Examples 3, 4, 9).

Example 16 (Comparative) Preparation of Polyimide Based onBPDA//3,4′-ODA/PPD//PA 95//90/10//10—(95% of Stoichiometric Dianhydride)

In a similar manner to Example 1, a polyimide was prepared with 11.5202g BPDA, 7.4278 g 3,4′-ODA,. 0.4457 g PPD and 0.6105 g phthalicanhydride. DSC analysis (10° C./min) of the resulting polyimide showed amelting point of 394° C. during the first heating scan, acrystallization exotherm upon the subsequent cooling scan at 323° C.,and a melting point of 391° C. during the subsequent reheat scan,indicating recoverable crystallinity from the melt, but too high amelting point.

Example 17 (Comparative) Preparation of the Polyimide Based onBPDA//3,4′-ODA//PA 93//100/14—(93% of Stoichiometric Dianhydride)

The diamine (3,4′-ODA), dianhydride (BPDA) and phthalic anhydride wereweighed directly into a 3 liter nitrogen purged resin kettle in theamounts listed in the table below. The resin kettle was then fitted witha three neck cover, an overhead mechanical stirring system (Cole-PalmerMaster Servodyne electric drive with a 50:1 gear ratio and a Hastelloymixing blade) and nitrogen purge. The apparatus was assembled and thefinely powdered monomers were mixed in the vessel for one hour at roomtemperature under inert gas purge.

To initiate melt polymerization, the kettle was lowered, via hydrauliclab jack, into a liquid metal bath (Patriot Alloys, Alloy-281) preheatedto 280° C. by a 220 volt band heater. The following thermal schedule(bath temperature) was followed during the polymerization:

TIME (MIN) TEMPERATURE (° C.) 0 280  0-26 280-400 26-44 400 44-64400-425 64-75 425

Polymerization was observed to proceed upon melting of the monomers andthe water of imidization was conveniently removed from the reactor viainert gas purge. Melt viscosity increased dramatically during the courseof the polymerization. Total polymerization time was 75 minutes.

At the conclusion of the polymerization, the heat source was removed andthe viscous polymer was manually discharged from the reaction vessel andallowed to cool to room temperature. The polymer exhibited a T_(g)=244°C., T_(c)=262° C. with H_(c)=23 J/g, T_(m)=391° C. with H_(m)=27 J/g byDSC analysis (20° C./min.).

Monomers Abbreviation Amount (g) Moles 3,4′-oxydianiline (3,4′-ODA)320.38 1.600 3,3′,4,4′-biphenyltetracarboxylic (BPDA) 437.77 1.488dianhydride phthalic Anhydride (PA) 33.18 0.224

Example 18 Preparation of the Polyimide Based onBPDA//APB-134/4,4′-ODA/PA 97/85.4/14.6/6—(97% of StoichiometricDianhydride)

A pre-blended powder mixture of approximately ten pounds of1,3-bis(4-aminophenoxy) benzene (APB-134, 4.10 lbs., 6.37 moles),4,4-oxydianiline (4,4′-ODA, 0.70 lbs., 1.59 moles),3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA, 5.00 lbs., 7.71moles), and phthalic anhydride (PA, 0.16 lbs., 0.49 moles) wascontinuously fed through an inlet opening of a Berstorff ZE-25 (25 mm)twin-screw extruder (Berstorff Corp., Florence, Ky.) into the firstbarrel zone maintained at 15° C. by circulating cooling water. Thescrews were continuously turning at 100 RPM. The reaction mixture wasconveyed through the cooled first zone and the next three barrel zonesmaintained at temperatures of 105° C., 150 to 175° C. and 200 to 225° C.respectively. The reaction mixture continued on through a fifth zonehaving an opening in the upper section of the wall and maintained at atemperature of 250 to 275° C., where water of reaction was continuouslyremoved through the opening provided. The reaction mixture was furtherconveyed through zone number six that was maintained at 300 to 325° C.,and on through zone seven at 340 to 350° C. where a second opening inthe upper section of the wall where the final amount of water ofreaction and/or bubbles that may have been formed in the mixture wereremoved. An eighth zone maintained at 350 to 360° C. then led to a diedischarge where the polyimide product was continuously extruded.Polyimide polymer produced an intrinsic viscosity in phenolic media of0.88 dl. per gram.

This polyimide was subjected to DSC analysis and exhibited in the firstheat scan a glass transition temperature of 195° C., a crystallizationtemperature of 255° C., and a melting point of 369° C. and exhibited inthe second heat scan a glass transition temperature of 201° C., acrystallization temperature of 274° C., and a melting point of 367° C.This polyimide exhibited a melt index of 22.7 when measured at 375° C.

A second independent run was made as described above in this Example(18). This resulting polyimide was subjected to DSC analysis andexhibited in the first heat scan a glass transition temperature of 194°C., a crystallization temperature of 261° C., and a melting point of372° C. and exhibited in the second heat scan a glass transitiontemperature of 206° C., a crystallization temperature of 266° C., and amelting point of 370° C.

Example 19 Preparation of the Polyimide Based onBPDA//APB-134/4,4′-ODA/PA 97/85.6/14.4/6—(97% of StoichiometricDianhydride)

Example 18 was repeated except that the Berstorff twin-screw extruderwas extended with two additional barrel zones. Approximately six poundsof 1,3-bis(4-aminophenoxy) benzene (APB-134, 2.45 lbs., 3.81 moles),4,4′-oxydianiline (4,4′-ODA, 0.42 lb., 0.95 mole),3,3′4,4′-biphenyltetracarboxylic dianhydride (BPDA, 3.00 lbs., 4.63moles), and phthalic anhydride (PA, 0.09 lb., 0.26 mole) wascontinuously fed through an inlet opening of the same Berstorfftwin-screw extruder into the first barrel zone maintained at 15° C. bycirculating cooling water. This first zone was maintained at 15° C. bycirculating cooling water. The screws were continuously turning at 100RPM. The reaction mixture was conveyed through the cooled first zone andthe next two barrel zones maintained at temperatures of 90° C. and 150°C., respectively. The reaction mixture continued on through a fourthzone maintained at a temperature of 250° C., and having an opening inthe upper section of the wall where water of reaction was continuouslyremoved through the opening provided. The reaction mixture was furtherconveyed through a fifth zone maintained at 300° C., and then on throughthe sixth and seventh zones with each maintained at temperature of 350°C., and with each having an opening in the upper section of the walls,the second and third such openings, where water of reaction wascontinuously removed. The reaction mixture was further conveyed throughzone number eight that was maintained at 360° C., and on through zonenine at 370° C. where a fourth opening in the upper section of the wallwhere the final amount of water of reaction and/or bubbles that may havebeen formed in the mixture were removed. A tenth zone maintained at 370°C. then led to a die discharge where the polyimide product wascontinuously extruded. Polyimide polymer produced an intrinsic viscosityin phenolic media of 0.82 dl. per gram.

This polyimide was subjected to DSC analysis and exhibited in the firstheat scan a glass transition temperature of 192° C., a crystallizationtemperature of 264° C., and a melting point of 368° C. and exhibited inthe second heat scan a glass transition temperature of 200° C., acrystallization temperature of 293° C., and a melting point of 360° C.This polyimide exhibited a melt index of 6.0 when measured at 350° C.,and 13.2 when measured at 375° C.

Example 20 Preparation of the Polyimide Based onBPDA//APB-134/4,4′-ODA/PA 97/85.5/14.5/6—(97% of StoichiometricDianhydride)

Example 19 was repeated except that the monomer ingredients wereindividually fed from four separate loss-in-weight feeders.Approximately 16.5 pounds of a monomer mixture consisting of 10.56 molesof 1,3-bis(4-aminophenoxy) benzene (APB-134), 2.61 moles of4,4-oxydianiline (4,4′-ODA), 12.76 moles of3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 0.77 mole ofphthalic anhydride (PA) were continuously fed from four separateloss-in-weight feeders at a total combined rate of 37.8 grams per minutethrough an inlet opening of the aforementioned extended Berstorfftwin-screw extruder into the first barrel zone. The screws werecontinuously turning at 100 RPM. The reaction mixture was conveyedthrough the cooled first zone and the next two barrel zones maintainedat temperatures of 90° C. and 150° C., respectively. The reactionmixture continued on through a fourth zone maintained at a temperatureof 250° C., and having an opening in the upper section of the wall wherewater of reaction was continuously removed through the opening provided.The reaction mixture was further conveyed through a fifth zonemaintained at 300° C., and then on through the sixth and seventh zoneswith each maintained at temperature of 350° C., and with each having anopening in the upper section of the walls, the second and third suchopenings, where water of reaction was continuously removed. The reactionmixture was further conveyed through zone number eight that wasmaintained at 350° C., and on through zone nine at 360° C. where afourth opening in the upper section of the wall where the final amountof water of reaction and/or bubbles that may have been formed in themixture were removed. A tenth zone maintained at 370° C. then led to adie discharge where the polyimide product was continuously extruded. Theresulting polyimide polymer exhibited an intrinsic viscosity in phenolicmedia of 0.72 dl. per gram.

This polyimide was subjected to DSC analysis and exhibited in the firstheat scan a glass transition temperature of 198° C., a crystallizationtemperature of 257° C., and a melting point of 370° C. and exhibited inthe second heat scan a glass transition temperature of 188° C., acrystallization temperature of 257° C., and a melting point of 371° C.This polyimide exhibited a melt index of 45.8 when measured at 375° C.

Example 21 Preparation of Polyimide Based on BPDA//APB-134/4,4′-ODA/PA95//80/20/10—(95% of Stoichiometric Dianhydride)

In a similar manner to Example 1, a polyimide was prepared with 8.2329 gof APB-134 and 1.4098 g 4,4′-ODA as codiamines, 9.8394 g of BPDA, and0.5214 g of PA. DSC analysis (10° C./min.) of the resulting polyimideshowed a melting point of 369° C. during the first heating scan, acrystallization exotherm upon the subsequent cooling at 306° C. and amelting point of 369° C. during the subsequent reheat indicatingrecoverable crystallinity from the melt.

Example 22 Preparation of Polyimide Based on BPDA//APB-134/4,4′-ODA/PA95//70/30/10—(95% of Stoichiometric Dianhydride)

In a similar manner to Example 1, a polyimide was prepared with 7.3225 gof APB-134 and 2.1495 g 4,4′-ODA as codiamines, 10.0016 g of BPDA, and0.5299 g of PA. DSC analysis (10° C./min.) of the resulting polyimideshowed a melting point of 364° C. during the first heating scan, acrystallization exotherm upon the subsequent cooling at 360° C. and acrystallization peak at 305° C. followed by a melting point of 365° C.during the subsequent reheat indicating recoverable crystallinity fromthe melt. There also was, however, DSC evidence for a high melting phaseat temperatures >400° C. at this level of 4,4′-ODA which would likely bedetrimental in terms of flow properties.

Example 23 Preparation of Polyimide Based onBPDA//APB-134/4,4′-ODA/MPD/PA 95//80/10/10/10—(95% of StoichiometricDianhydride)

In a similar manner to Example 1, a polyimide was prepared with 8.3686 gof APB-134, 0.7165 g 4,4′-ODA and 0.3869 g MPD as codiamines, 10.0016 gof BPDA, and 0.5299 g of PA. DSC analysis (10° C./min.) of the resultingpolyimide showed a melting point of 362° C. during the first heatingscan, a crystallization exotherm upon the subsequent cooling at 311° C.,and a crystallization peak at 276° C. followed by a melting point of358° C. during the subsequent reheat indicating recoverablecrystallinity from the melt.

Example 24 Preparation of Polyimide Based onBPDA//APB-134/4,4′-ODA/MPD/PA 95//75/20/5/10—(95% of StoichiometricDianhydride)

In a similar manner to Example 1, a polyimide was prepared with 7.8454 gof APB-134, 1.4330 g 4,4′-ODA and 0.1935 g MPD as codiamines, 10.0014 gof BPDA, and 0.5301 g of PA. DSC analysis (10° C./min.) of the resultingpolyimide showed a melting point of 355° C. during the first heatingscan, a crystallization exotherm upon the subsequent cooling at 330° C.,and a crystallization peak at 277° C. followed by a melting point of354° C. during the subsequent reheat indicating recoverablecrystallinity from the melt.

Example 25 (Comparative) Preparation of Polyimide Based onBPDA//APB-134/4,4′-ODA/MPD/PA 95//70/20/10/10—(95% of StoichiometricDianhydride)

In a similar manner to Example 1, a polyimide was prepared with 7.4452 gof APB-134, 1.4570 g 4,4′-ODA and 0.3934 g MPD as codiamines, 10.1691 gof BPDA, and 0.5389 g of PA. DSC analysis (10° C./min.) of the resultingpolyimide showed a melting point of 343° C. during the first heatingscan, a crystallization exotherm upon the subsequent cooling at 316° C.,and a melting point of 320° C. during the subsequent reheat indicatingrecoverable crystallinity from the melt. The degree of crystallinity inthis sample, however, was significantly reduced after the initialheating run.

Example 26 Preparation of Polyimide Based on BPDA//APB-134/MPD/PA95//80/20/10—(95% of Stoichiometric Dianhydride)

In a similar manner to Example 1, a polyimide was prepared with 8.5088 gof APB-134 and 0.7868 g MPD as codiamines, 10.1691 g of BPDA, and 0.5388g of PA. DSC analysis (10° C./min.) of the resulting polyimide showed amelting point of 359° C. during the first heating scan, nocrystallization exotherm upon the subsequent cooling, and acrystallization peak at 298° C. followed by a melting point of 355° C.during the subsequent reheat indicating recoverable crystallinity fromthe melt. There also was, however, DSC evidence for a high melting phaseat temperatures >400° C. at this level of MPD which could be detrimentalin terms of flow properties.

Example 27 Preparation of Polyimide Based on BPDA//APB-134/3,4′-ODA/PA95//80/20/10—(95% of Stoichiometric Dianhydride)

In a similar manner to Example 1, a polyimide was prepared with 8.2329 gof APB-134 and 1.4098 g 3,4′-ODA as codiamines, 9.8394 g of BPDA, and0.5214 g of PA. DSC analysis (10° C./min.) of the resulting polyimideshowed a melting point of 366° C. during the first heating scan, acrystallization exotherm upon the subsequent cooling at 302° C. and amelting point of 367° C. during the subsequent reheat indicatingrecoverable crystallinity from the melt.

Example 28 Preparation of Polyimide Based on BPDA//APB-134/3,4′-ODA/PA95//75/25/10—(95% of Stoichiometric Dianhydride)

In a similar manner to Example 1, a polyimide was prepared with 7.7813 gof APB-134 and 1.7766 g 3,4′-ODA as codiamines, 9.9197 g of BPDA, and0.5257 g of PA. DSC analysis (10° C./min.) of the resulting polyimideshowed a melting point of 360° C. during the first heating scan, acrystallization exotherm upon the subsequent cooling at 316° C. and acrystallization peak at 237° C. followed by a melting point of 358° C.during the subsequent reheat indicating recoverable crystallinity fromthe melt.

Example 29 Preparation of Polyimide Based on BPDA//APB-134/3,4′-ODA/PA95//70/30/10—(95% of Stoichiometric Dianhydride)

In a similar manner to Example 1, a polyimide was prepared with 7.3225 gof APB-134 and 2.1495 g 3,4′-ODA as codiamines, 10.0016 g of BPDA, and0.5299 g of PA. DSC analysis (10° C./min.) of the resulting polyimideshowed a melting point of 353° C. during the first heating scan, acrystallization exotherm upon the subsequent cooling at 313° C. and acrystallization peak at 246° C. followed by a melting point of 350° C.during the subsequent reheat indicating recoverable crystallinity fromthe melt.

Example 30 Preparation of Polyimide Based on BPDA//APB-134/3,4′-ODA/PA95//60/40/10—(95% of Stoichiometric Dianhydride)

In a similar manner to Example 1, a polyimide was prepared with 6.3816 gof APB-134 and 2.9141 g 3,4′-ODA as codiamines, 10.1691 g of BPDA, and0.5389 g of PA. DSC analysis (10° C./min.) of the resulting polyimideshowed a melting point of 335° C. during the first heating scan, acrystallization exotherm upon the subsequent cooling at 313° C. and acrystallization peak at 266° C. followed by a melting point of 338° C.during the subsequent reheat indicating recoverable crystallinity fromthe melt.

Example 31 (Comparative) Preparation of Polyimide Based onBPDA//APB-134/APB-144/PA 95//80/20/10—(95% of StoichiometricDianhydride)

In a similar manner to Example 1, a polyimide was prepared with 7.9744 gof APB-134 and 1.9936 g APB-144 as codiamines, 9.5304 g of BPDA, and0.5051 g of PA. DSC analysis (10° C./min.) of the resulting polyimideshowed a melting point of 390° C. during the first heating scan, acrystallization exotherm upon the subsequent cooling at 344° C. and amelting point of 390° C. during the subsequent reheat indicatingrecoverable crystallinity from the melt. The use of APB-144 incombination with APB-134 was apparently not as effective as the othercodiamines in reducing the melting point into a more useable range.

Example 32 Preparation of Polyimide Based on BPDA//APB-134/BAPS/PA95//80/20/10—(95% of Stoichiometric Dianhydride)

In a similar manner to Example 1, a polyimide was prepared with 7.6107 gof APB-134 and 2.8148 g BAPS as codiamines, 9.0958 g of BPDA, and 0.4820g of PA. DSC analysis (10° C./min.) of the resulting polyimide showed amelting point of 355° C. during the first heating scan, acrystallization exotherm upon the subsequent cooling at 270° C. and acrystallization peak at 294° C. followed by a melting point of 350° C.during the subsequent reheat indicating recoverable crystallinity fromthe melt.

Example 33 (Comparative) Preparation of Polyimide Based onBPDA//APB-134/2Ph-APB-144/PA 95//80/20/10—(95% of StoichiometricDianhydride)

In a similar manner to Example 1, a polyimide was prepared with 7.7727 gof APB-134 and 2.4497 g 2Ph-APB-144 as codiamines, 9.2894 g of BPDA, and0.4935 g of PA. DSC analysis (10° C./min.) of the resulting polyimideshowed a melting point of 351° C. during the first heating scan, nocrystallization exotherm upon the subsequent cooling and no meltingpoint during the subsequent reheat indicating that the crystallinity inthis sample was not readily recoverable from the melt.

Example 34 (Comparative) Preparation of Polyimide Based onBPDA//APB-134/2Ph-APB-144/PA 95//70/30/10—(95% of StoichiometricDianhydride)

In a similar manner to Example 1, a polyimide was prepared with 6.7177 gof APB 134 and 3.6281 g 2Ph-APB-144 as codiamines, 9.1734 g of BPDA, and0.4870 g of PA. DSC analysis (10° C./min.) of the resulting polyimideshowed a melting point of 327° C. during the first heating scan, nocrystallization exotherm upon the subsequent cooling and no meltingpoint during the subsequent reheat indicating that the crystallinity inthis sample was not readily recoverable from the melt.

What is claimed is:
 1. A melt-processible, thermoplastic copolyimidecomprising a reaction product of components consisting essentially of:(I) an aromatic dianhydride component of3,3′4,4′-biphenyltetracarboxylic dianhydride (BPDA); (II) an aromaticdiamine component consisting essentially of: (A) a first aromaticdiamine selected from the group consisting of1,3-bis(4-aminophenoxy)benzene (APB-134) and 3,4′-oxydianiline(3,4′-ODA); (B) a second aromatic diamine selected from the groupconsisting of 1,3-bis(4-aminophenoxy)benzene (APB-1 34),3,4′-oxydianiline (3,4′-ODA), 1,3-bis(3-aminophenoxy)benzene (APB-133),4,4′-oxydianiline (4,4′-ODA), 1,4-bis(4-aminophenoxy) benzene (APB-144),3-diaminobenzene (MPD), 4,4′-bis(4-aminophenoxy)diphenyl sulfone (BAPS),4,4′-bis(4-aminophenoxy)-biphenyl (BAPB),2,2-bis(4-[4-aminophenoxyl]phenyl)propane (BAPP),bis(4-[4-aminophenoxy]phenyl ether (BAPE), 4,4′-oxydianiline (4,4′-ODA)and 1,3-diaminobenzene (MPD) in combination, and 4,4′-oxydianiline(4,4′-ODA) and 1,4-diaminobenzene (PPD) in combination;  with theproviso that the second diamine is not the same as the first diamine;and (III) an endcapping component; wherein the copolyimide has astoichiometry in the range from 93% to 98%, exhibits a melting point inthe range of 330° C. to 385° C., and exhibits reoverable crystallinityas determined by differential scanning calorimetry analysis.
 2. Thecopolyimide of claim 1 wherein the aromatic dianhydride component is3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), the first aromaticdiamine component is 1,3-bis(4-aminophenoxy)benzene (APB-134), thesecond aromatic diamine component is 3,4′-oxydianiline (3,4′-ODA), andthe molar ratio of 1,3-bis(4-aminophenoxy)benzene/3,4′-oxydianiline(APB-134/3,4′-ODA) is in the range from about 90/10 to about 60/40. 3.The copolyimide of claim 1 wherein the aromatic dianhydride component is3,3′4,4′-biphenyltetracarboxylic dianhydride (BPDA), the first aromaticdiamine component is 3,4′-oxydianiline (3,4′-ODA), the second aromaticdiamine component is 1,3-bis(4-aminophenoxy)benzene (APB-134), and themolar ratio of 3,4′-oxydianiline/1,3-bis(4-aminophenoxy)benzene(3,4′-ODA/APB-134) is in the range from about 95/5 to about 60/40. 4.The copolyimide of claim 1 wherein the aromatic dianhydride component is3,3′4,4′-biphenyltetracarboxylic dianhydride (BPDA), the first aromaticdiamine component is 1,3-bis(4-aminophenoxy)benzene (APB-134), thesecond aromatic diamine component is 4,4′-oxydianiline (4,4′-ODA), andthe molar ratio of 1,3-bis(4-aminophenoxy)benzene/4,4′-oxydianiline(APB-134/4,4′-ODA) is in the range from about 90/10 to about 75/25. 5.The copolyimide of claim 1 wherein the aromatic dianhydride component is3,3′4,4′-biphenyltetracarboxylic dianhydride (BPDA), the first aromaticdiamine component is 1,3-bis(4-aminophenoxy)benzene (APB-134), thesecond aromatic diamine component is 1,3-diaminobenzene (MPD), and themolar ratio of 1,3-bis(4-aminophenoxy)benzene/1,3-diaminobenzene(APB-134/MPD) is in the range from about 95/5 to about 85/15.
 6. Thecopolyimide of claim 1 wherein the aromatic dianhydride component is3,3′4,4′-biphenyltetracarboxylic dianhydride (BPDA), the first aromaticdiamine component is 1,3-bis(4-aminophenoxy)benzene (APB-134), thesecond aromatic diamine component is X, wherein X is selected from thegroup consisting of 4,4′,bis(4-aminophenoxy)diphenyl sulfone (BAPS),4,4′-bis(4-aminophenoxy)-biphenyl (BAPB),2,2-bis(4-[4-aminophenoxyl]phenyl)propane (BAPP), andbis(4-[4-aminophenoxy]phenyl ether (BAPE), and the molar ratio of1,3-bis(4-aminophenoxy)benzene/X (APB-134/X) is in the range from about95/5 to about 75/25.
 7. The copolyimide of claim 1 wherein the aromaticdianhydride component is 3,3′4,4′-biphenyltetracarboxylic dianhydride(BPDA), the first aromatic diamine component is1,3-bis(4-aminophenoxy)benzene (APB-134), the second aromatic diaminecomponent is 1,3-bis(3-aminophenoxy)benzene (APB-133), and the molarratio of 1,3-bis(4-aminophenoxy)benzene/1,3-bis(3-aminophenoxy)benzene(APB-134/APB-133) is in the range from about 95/5 to about 85/15.
 8. Thecopolyimide of claim 1 wherein the aromatic dianhydride component is3,3′4,4′-biphenyltetracarboxylic dianhydride (BPDA), the first aromaticdiamine component is 3,4′-oxydianiline (3,4′-ODA), the second aromaticdiamine component is 4,4′-oxydianiline (4,4′-ODA), and the molar ratioof 3,4′-oxydianiline/4,4′-oxydianiline (3,4′-ODA/4,4′-ODA) is in therange from about 85/15 to about 70/30.
 9. The copolyimide of claim 1wherein the aromatic dianhydride component is3,3′4,4′-biphenyltetracarboxylic dianhydride (BPDA), the first aromaticdiamine component is 3,4′-oxydianiline (3,4′-ODA), the second aromaticdiamine component is APB-144 and the molar ratio of 3,4′-ODA/APB-144 isin the range from about 95/5 to about 65/35.
 10. The copolyimide ofclaim 1 wherein the aromatic dianhydride component is3,3′4,4′-biphenyltetracarboxylic dianhydride (BPDA), the first aromaticdiamine component is 3,4′-oxydianiline (3,4′-ODA), the second aromaticdiamine component is Y, wherein Y is selected from the group consistingof 4,4′,bis(4-aminophenoxy)diphenyl sulfone (BAPS),4,4′-bis(4-aminophenoxy)-biphenyl (BAPB), bis(4-[4-aminophenoxy]phenylether (BAPE), and 2,2-bis(4-[4-aminophenoxyl]phenyl)propane (BAPP), andthe molar ratio of 1,3-bis(4-aminophenoxy)benzene/Y (APB-134/Y) is inthe range from about 95/5 to about 70/30.
 11. The copolyimide of claim 1wherein the aromatic dianhydride component is3,3′4,4′-biphenyltetracarboxylic dianhydride (BPDA), the first aromaticdiamine component is 3,4′-oxydianiline (3,4′-ODA), the second aromaticdiamine component is 1,3-bis(3-aminophenoxy)benzene (APB-133), and themolar ratio of 3,4′-oxydianiline /1,3-bis(3-aminophenoxy)benzene(3,4′-ODA/APB-133) is in the range from about 95/5 to about 85/15. 12.The copolyimide of claim 1 wherein the aromatic dianhydride component is3,3′4,4′-biphenyltetracarboxylic dianhydride (BPDA), the first aromaticdiamine component is 1,3-bis(4-aminophenoxy)benzene (APB-134), thesecond aromatic diamine component is 4,4′-oxydianiline (4,4′-ODA) and1,3-diaminobenzene (MPD)in combination,and the molar parts of1,3-bis(4-aminophenoxy)benzene/4,4′-oxydianiline/1,3-diaminobenzene(APB-134/4,4′-ODA/MPD) range from about 95/2.5/2.5 to about 75/20/5. 13.The copolyimide of claim 1 wherein the aromatic dianhydride component is3,3′4,4′-biphenyltetracarboxylic dianhydride (BPDA), the first aromaticdiamine component is 1,3-bis(4-aminophenoxy)benzene (APB-134), thesecond aromatic diamine component is 4,4′-oxydianiline (4,4′-ODA) and1,4-diaminobenzene (PPD) in combination,and the molar parts of1,3-bis(4-aminophenoxy)benzene/4,4′-oxydianiline/1,3-diaminobenzene(APB-134/4,4′-ODA/PPD) range from about 90/5/5 to about 70/20/10. 14.The copolyimide of claim 1 wherein the aromatic dianhydride component is3,3′4,4′-biphenyltetracarboxylic dianhydride (BPDA), the first aromaticdiamine component is 3,4′-oxydianiline (3,4′-ODA), the second aromaticdiamine component is 4,4′-oxydianiline (4,4′-ODA) and 1,4-diaminobenzene(PPD) in combination, and the molar parts of3,4′-oxydianiline/4,4′-oxydianiline/1,4-diaminobenzene(3,4′-ODA/4,4′-ODA/PPD) range from about 95/2.5/2.5 to about 70/20/10.15. A process of preparing a melt processible polyimide composition bymelt polymerization comprising the steps of: (a) blending, tosubstantial homogeneity, components comprising: (I) 93 to 98 mole partsof an aromatic dianhydride component consisting essentially of3,3′4,4′-biphenyltetracarboxylic dianhydride (BPDA); (II) 100 mole partsof an aromatic diamine component consisting essentially of: (A) a firstaromatic diamine selected from the group consisting of1,3-bis(4-aminophenoxy)benzene (APB-134) and 3,4′-oxydianiline(3,4′-ODA); (B) a second aromatic diamine selected from the groupconsisting of 1,3-bis(4-aminophenoxy)benzene (APB-1 34),3,4′-oxydianiline (3,4′-ODA), 1,3-bis(3-aminophenoxy)benzene (APB-133),4,4′-oxydianiline (4,4′-ODA), 1,4-bis(4-aminophenoxy)benzene (APB-144),1,3-diaminobenzene (MPD), 4,4′,bis(4-aminophenoxy)diphenyl sulfone(BAPS), 4,4′-bis(4-aminophenoxy)-biphenyl (BAPB),2,2-bis(4-[4-aminophenoxyl]phenyl)propane (BAPP),bis(4-[4-aminophenoxy]phenyl ether (BAPE), 4,4′-oxydianiline (4,4′-ODA)and 1,3-diaminobenzene (MPD) in combination, and 4,4′-oxydianiline(4,4′-ODA) and 1,4-diaminobenzene (PPD) in combination;  with theproviso that the second diamine is not the same as the first diamine;and (III) 4 to 14 mole parts of at least one endcapping component; thecomponents (I), (II) and (III) being in substantially solventless formand the blending step producing a substantially solventless componentblend; the blending step being carried out at a temperature below themelting point of any of components (I), (II) and (III); the component(I) and (II) being present in the component blend in a molar ratio of(I):(II) from 0.93 to 0.98; the component (III) being present in thecomponent blend in a molar ratio (III):(II) of 0.04 to 0.14; (b) heatingthe substantially solventless component blend produced in step (a) to apredetermined melt processing temperature at which the (I) aromaticdianhydride component and the (II) aromatic diamine component are meltedand will react to form a melt of a polyimide; the predetermined meltprocessing temperature being less than the temperature at which thepolyimide melt chemically decomposes; (c) mixing the component blend andthe polyimide melt produced therefrom during said heating step (b); (d)removing water of reaction from the component blend and the polyimidemelt produced therefrom during the heating step (b); (e) forming thepolyimide melt into an article having predetermined shape; and (f)cooling the article having predetermined shape to ambient temperature;wherein the polyimide exhibits a melting point in the range of 330° C.to 385° C., and the polyimide exhibits recoverable crystallinity asdetermined by DSC analysis.
 16. The process of claim 15 wherein theendcapping component is selected from the group consisting of phthalicanhydride, naphthalic anhydride, and aniline.
 17. The process of claim15 wherein the article having predetermined shape is selected from thegroup consisting of a film, a fiber, an extrudate, a pellet, acompression-molded article, and a blow-molded article.
 18. The processof claim 15 wherein the steps (a)-(e) are carried out in an extruder.19. The process of claim 19 wherein the extruder defines sequentialzones 1 through x, where x is about 2 to about 10, the component blendand the polyimide melt produced therefrom being passed through thesequential zones, each of the zones being heated to a temperature lessthan the predetermined melt processing temperature, the blending step(a) being carried out in zone 1 at a temperature which is less than themelting temperature of each of the components (I), (II), and (III).